The present invention relates to a method of constructing an output correction database indicating output characteristics of a plurality of load measurement sensing devices such as strain gauge sensors, or the like, in the condition that the sensing devices are attached to a vehicle such as a truck, ship, train, airplane, or the like, so that the database is used for calculating correction values for correcting vehicle characteristics, or the like, in which loads imposed on the respective sensing devices are changed in accordance with the variations in output characteristics of the sensing devices and the structure of the vehicle, when the load of the vehicle is measured on the basis of the sum of the outputs of the sensing devices, or the like. The present invention further relates to a weight vessel adapted to be used when the database is constructed by the above method.
The measurement of load of a vehicle may be provided for a large-sized vehicle such as a truck, etc., for example, for the purpose of preventing traffic accidents such as rolling accidents caused by overload, etc., and preventing acceleration of deterioration of the vehicle.
Conventionally, the measurement of load of a vehicle is performed in the condition that the vehicle, which is a subject of the measurement, is placed on a platform weighing machine so called xe2x80x9cKANKANxe2x80x9d in Japanese. However, because a large-scaled equipment and a large installation space are required for the measurement, the number of platform weighing machines allowed to be installed in the space is limited so that numbers of vehicles cannot be measured. Furthermore, the cost for installing the platform weighing machines increases.
Recently, therefore, a load measuring apparatus which is mounted on the vehicle per se to measure the load of the vehicle is provided.
In an on-vehicle type conventional load measuring apparatus, for example, load measurement sensing devices such as strain gauge sensors, or the like, are designed to be attached to suitable positions between front, rear, left and right places of carrier frames and circular-arc-like leaf springs interposed between left and right opposite end portions of front and rear axles so that the load is measured on the basis of the sum of signals outputted from the sensing devices respectively proportional to the loads imposed on the front, rear, left and right sensing devices.
When the outputs of the respective sensing devices are used directly for the measurement of the load of the vehicle by the aforementioned load measuring apparatus, the outputs of the sensing devices may become values which do not correspond to the loads actually imposed on the respective sensing devices because of the variations in the output characteristics of the sensing devices even in the case where the center of gravity of a baggage is located substantially at a center of a carrier so that the load from the baggage or carrier is evenly imposed on the respective sensing devices. That is, there is a risk that the correct values of the load of the baggage placed on the carrier cannot be obtained on the basis of the sum of the outputs of the respective sensing devices.
Further, the outputs of the sensing devices depend also on vehicle characteristics defined in accordance with the structure of the vehicle.
In measurement of a load on a vehicle by using such a plurality of sensing devices, it becomes necessary to correct the outputs of the sensing devices in accordance with the individual output characteristics and vehicle characteristics.
As described above, calculation of correction values for correcting the output characteristics of the respective sensing devices and calculation of the output correction values of the respective sensing devices in accordance with the vehicle characteristics are performed on the basis of calculation of coefficients to make the sum of the outputs of the respective sensing devices accord with a value corresponding to a known load value in the condition that the value of the load on the carrier is known. Particularly, correction values corresponding to the output characteristics of the sensing devices are calculated after the loaded state is adjusted so that the center of gravity of the carrier in the loaded state is made coincident with the center of gravity of the carrier in the tare or non-loaded state.
Both the calculation of the output characteristics of the sensing devices and the calculation of the output correction values of the sensing devices in accordance with the vehicle characteristics are performed each time by suitably increasing/decreasing the weight value of a weight on the carrier.
That is, the calculation of the output correction values of the load measurement sensing devices is equivalent to the calculation of correction values or correction equations for the sensing devices on the basis of a database constructed by calculation of the changes of the output characteristics of the respective sensing devices corresponding to the weight. It is therefore necessary to fetch the outputs of the respective sensing devices to construct the database while the load on the carrier is increased/decreased gradually and while the load per se after the increase/decrease is always made known.
Therefore, in order to make the load per se after increased/decreased always known while the load of the carrier is increased/decreased gradually at the time of the work of calculating the output correction values, it is considered that weights such as balance weights. etc., each having a known mass value are placed on a single position or a plurality of places on the carrier so that the load is evenly imposed on the sensing devices and the number of weights per place is increased/decreased equally whenever the outputs of the sensing devices have been measured and fetched as data.
Because such balance weights to be used by being mounted on the carrier are, however, large both in weight and in external size, a conveying apparatus such as a forklift, a crane, etc. must be used separately for carrying the balance weights and increasing/decreasing the number of the balance weights on the carrier. Accordingly, there is a disadvantage that not only surplus labor and equipment are required but also dangerous work such as slinging work for the balance weights must be carried out in the case of a crane.
Further, the weight per balance weight is predetermined so that the pitch for increasing/decreasing the load is limited by the predetermined balance weight. There arises a disadvantage that the change of the output of each sensing device cannot be calculated in a pitch smaller than the weight of one balance weight or various kinds of balance weights different in weight must be prepared in order to calculate the change of the output in a pitch as small as possible.
Taking the aforementioned circumstances into consideration, a first object of the present invention is to provide a method of constructing a database for correcting outputs of a plurality of load measurement sensing devices such as strain gauge sensors, etc., for measuring load of a vehicle so that the database is used for calculating correction values for correcting the outputs of the sensing devices in accordance with output characteristics of the sensing devices and vehicle characteristics, and so that the database indicating the output characteristics of the sensing devices can be constructed by simple labor.
A second object of the present invention is to provide a weight vessel adapted for carrying out the database constructing method so that the weight can be changed in a desired arbitrary pitch without requiring any surplus labor, any equipment such as balance weights, and any dangerous work.
In order to achieve the above first object, according to the present invention, there is provided a method of constructing an output characteristic correction database indicating output characteristics of a plurality of load measurement sensing devices disposed in a vehicle at portions supporting a carrier of the vehicle so that the database is to be used to calculate correction values for correcting the outputs of the sensing devices in accordance with vehicle characteristics determined on the basis of variations in output characteristic of the sensing devices and a structure of the vehicle, comprising the steps of: changing an amount of a liquid contained in a weight vessel placed on the carrier to thereby change weight of the weight vessel containing the liquid while making a value of the weight of the weight vessel containing the liquid known; and collecting and storing at least one of the amount of the liquid and the weight of the weight vessel while relating it to the outputs of the sensing devices whenever the amount of the liquid in the weight vessel is changed.
In the above method of constructing a database for correcting outputs of load measurement sensing devices, according to the present invention, a plurality of the weight vessels are placed at lengthwise and widthwise equal intervals on the carrier; and the outputs of the sensing devices are collected and stored so as to be related to at least one of the amounts of the liquid in the weight vessels and the weight values of the weight vessels in a condition that the weight values of the weight vessels are made equal to each other.
In order to achieve the above second object, according to the present invention, the above-mentioned weight vessel comprises: a vessel body shaped like a hollow box so that a liquid can be reserved in the inside of the vessel body; an injection inlet formed in an upper portion of the vessel body; a discharge outlet formed in a lower portion of the vessel body; and a scale formed on a side portion of the vessel body so as to indicate a value corresponding to the amount of the liquid reserved in the vessel body; wherein at least the side portion provided with the scale in side portions of the vessel body is formed of a transparent or semitransparent member so that the amount of the liquid in the vessel body can be seen through the transparent or semitransparent member.
In the above weight vessel, according to the present invention, rotatable caster wheels are attached to at least three corner portions on a lower end of the vessel body to thereby make the vessel moveable.
In the above weight vessel, according to the present invention, shock absorbers are interposed between corner portions of the vessel body and the caster wheels respectively so that the shock absorbers can be expanded/contracted to come near to/go far from a ground surface of the caster wheels and so that the vessel body is urged to go far from the ground surface with respect to the caster wheels against loads of the vessel body and the liquid in the vessel body.
In the above weight vessel, according to the present invention, the shock absorbers are contracted to bring the vessel body into contact with the ground surface when the amount of the liquid in the vessel body reaches a predetermined value, and wherein contraction limiting members are further provided so that the contraction of the shock absorbers is limited in the condition that the vessel body is brought into contact with the ground surface.
In the method of constructing a database for connecting the outputs of load measurement sensing devices according to the present invention, the known weight of the weight vessel containing the liquid in the weight vessel is increased/decreased by increasing/decreasing the amount of the liquid in the weight vessel. Accordingly, the weights imposed on the sensing devices can be changed easily in an arbitrary pitch without requiring any troublesome balance weight increasing/decreasing work using a conveying apparatus such as a forklift, a crane, or the like, as in the conventional case where balance weights are used and without the necessity of separately preparing in advance various kinds of balance weights different in weight. Accordingly, the database indicating the changes of the output characteristics of the sensing devices corresponding to the changes of the weights imposed on the sensing devices can be constructed easily.
Further, in the method of constructing a database for correcting the outputs of the load measurement sensing devices according to the present invention, the balance of weight imposed on the carrier is made uniform by the plurality of weight vessels having weights made equal to each other. Accordingly, the changes of the weights in the output characteristics of the sensing devices containing the influence of the vehicle characteristics determined on the basis of the structure of the vehicle can be collected easily and stored in the form of a database.
Further, in the weight vessel according to the present invention, the amount of liquid reserved in a box-like vessel body can be confirmed easily by means of the scale provided at a side portion of the vessel body. Furthermore, by confirming the weight of the vessel body per se and the specific gravity of the liquid in advance, the weight of the whole of the vessel body can be calculated easily on the basis of the amount of the liquid in the vessel body observed by means of the scale.
Further, by making the vessel body empty, the weight vessel can be carried only with the light weight of the weight vessel per se. The weight vessel can be carried safely without use of any conveying apparatus such as a forklift, a crane, or the like, unlike the conventional case where balance weights are used. Further, the increase/decrease of the weight of the weight vessel can be performed easily by injecting the liquid into the vessel body through the injection inlet and discharging the liquid out of the vessel body through the discharge outlet.
Further, in the weight vessel according to the present invention as, by providing caster wheels at least at three corner portions so as to rotate on a lower end of the vessel body, the vessel body can be moved easily so as not to be lifted from the ground surface.
Further, in the weight vessel according to the present invention, the vessel body comes far from the ground surface of the caster wheels by the urging force of the shock absorbers. Accordingly, the carrying of the weight vessel can be performed easily by means of the rotation of the caster wheels.
Further, in the weight vessel according to the present invention, by making the amount of the liquid in the vessel body reach a predetermined value to make the shock absorbers contract, the vessel body is brought into contact with the ground surface. Accordingly, if the weight of the weight vessel is increased to some degree, the weight vessel can be fixed by the contact of the vessel body with the ground surface. Furthermore, the contraction of the shock absorbers is limited by the contraction limiting members in this condition. Accordingly, the shock absorbers are prevented from being worn out and being damaged in the continuous contracting state due to continuous reception of overload.